Photographic elements are often composed of many layers of photosensitive and non-photosensitive materials, with each layer making a unique contribution to achieve a high degree of image quality. In color photography especially, the number of emulsion-applied layers is often considerable, with, in addition to one or more layers being deposited to define the proper level for each of the primary colors, layers being present that are responsible for performing antihalation, filtering, barrier, antistatic, and antiblocking functions. These layers function more or less independently, and it is important that the various components of the layers not migrate into neighboring layers. If migration occurs, the loss of the component not only diminishes overall performance of the function for which it was added, but the migrated component also can interfere with the function of neighboring layers into which it has migrated. Migration is a serious problem in photography, and various means have been adopted to eliminate it. One means that has been utilized is to attach the migratable components in a layer to a relatively non-migratable species such as an organic polymer.
The [2H]-1,2,4-triazoline-3-thione (hereinafter referred to as triazolinethione) heterocycle, shown along with its tautomeric form (often referred to as mercapto triazole) in equation (1), is extremely useful in the photographic industry. ##STR1## For example, low molecular weight triazolinethione compounds have been utilized to enhance the contrast of images in silver photography (U.S. Pat. No. 3,307,944); as agents to inhibit overdevelopment of the outermost layer of a silver halide multilayer color construction (U.S. Pat. No. 3,615,522); as anti-bronzing agents to maintain a high degree of image intensity and contrast (U.S. Pat. No. 3,647,451); as stabilizers for developed images (U.S. Pat. No. 3,718,468); and as photosensitive agents for maintaining image contrast (U.S. Pat. No. 3,832,186). All these utilizations have involved relatively migratable, low molecular weight, i.e., of 200 or less, compounds.
In two instances the triazolinethione heterocycle has been incorporated into monomers which then undergo polymerization to afford heterocyclic polymers. An isopropenyl-functional monomer 1 (as described by Cr. Simionescu, et al., Acta Chim. Acad. Sci. Hung., 86, 459 (1975); Chem Abstr., 84, 44710v (1976)) was free-radically polymerized; the purpose of forming the polymer was not divulged. ##STR2## Bis(epoxide) monomer 2 was also disclosed (O. P. Shvaika, et al., USSR 765,267 (1978); Chem. Abstr., 94, 104319t (1981)) for use in epoxy resins to reduce the self-hardening temperature. ##STR3## In a third instance, M. I. Shtil'man, et al., Polymer Sci. USSR, 10, 2827 (1969), disclose a solventless, thermal cyclodehydration of one particular poly(acylthiosemicarbazide) 3 to form a poly([2H]-1,2,4-triazoline-3-thione) 4 according to equation (2). ##STR4##
We have examined the above cyclodehydration with other poly(acylthiosemicarbazides), however, and have found that often crosslinked poly(triazolinethiones) which are insoluble and intractable are the result.